This research program is designed to study the biochemical characteristics of lens proteins and their changes during the process of cataractogenesis. One objective is to determine whether the progression to opacity in the lenses is reversible. Rat lens is being employed as a model system. Attention is being paid to the changes of the alpha and gamma crystallins, of normal and cataract lenses, which are Fractions I and V, respectfully, in our Sephadex G-200, superfine, chromatogram. Progress has been made in defining the characteristics and the protein make-up of Fractions II and V. Fraction II, which is a novel group of proteins, exists in the normal lens, but is absent in the streptozotocin- and galactose-induced cataract lenses. The isolation, purification, and analysis of the major proteins in Fractions II and V is in progress. Employing antisera prepared from the pure proteins, studies are to be made on the antigenic properties of the protein fractions and on the reactions between the normal and cataract lens proteins. Protein-protein interaction studies will also be carried out to test the hypothesis that aggregation of lens proteins facilitates cataractogenesis.